PROJECT SUMMARY The major aim of this project is to develop and validate a norm referenced test of grammatical development that can be used in English. This tool will target 4-8;11 year old Spanish-, and Vietnamese - speaking ELLs with and without developmental language disorder (DLD). This will be directly useful for two of the largest groups of ELLs in the US. It will be also useful for children who speak languages related to Spanish or Vietnamese. We will achieve this aim by 1) evaluating current item-level data to guide development; 2) piloting an item set to include in item tryout; 3) conducting an item tryout study to establish an item set for testing morphosyntactic performance in ELLs; and 4) field testing and validating a set of morphosyntactic items for to differentiate among ELLs with DLD at different levels of language exposure/use. We will recruit 1,050 ELLs (525 per language pair) in the target age range from representative U.S. bilingual populations both in regard to language and SES. Children will complete a battery of index measures in their home language and English to identify DLD. They will complete testing in English on the proposed index measure targeting grammatical knowledge. This work furthers our research in DLD, especially with bilingual children. We will document a broad profile of language skills in two groups of ELLs whose first languages have distinct linguistic features (Vietnamese & Spanish) with and without DLD. The tool developed will transformative for the majority of SLPs who speak only English and will allow for timely identification and remediation of DLD in ELLs. It will also be useful for researchers who need to benchmark children's expected performance relative to English exposure in developmental and intervention studies. The proposed work builds on recent significant gains we have made in the correct classification of Spanish-English bilinguals with DLD through the identification of clinical markers of DLD. Yet, there continues to be significant health disparities associated with identification and treatment of DLD in bilingual populations. There is a critical need to develop tools that can be used with ELLs from other language backgrounds. We know that experiential factors (age of acquisition and language use) interact with bilingual language outcomes. We also know from the published literature that there are some differences in English language acquisition associated with the typology of the learner's first language, but we do not have normative data to inform diagnostic decisions about children from language backgrounds other than Spanish. Currently, the most accurate clinical decisions need to be made on the basis of 2 languages. The proposed project will extend the knowledge base regarding clinical markers of DLD from Spanish-speaking ELLs to examine markers of DLD in Vietnamese-speaking ELLs in the US context.